Figure 2.8: Geographical range for some TV White Space wireless standards (Source: [211]).
[Wireless regional Area Network (WRAN) Wireless Personal Area Network (WPAN), Wireless Local Area Network (WLAN), Wireless Metropolitan Area Network(WMAN), Wireless Wide Area Network(WWAN)]
IEEE 802.16 efforts especially in the developing world where according to [199] some 341 million people in sub-Saharan Africa lived beyond a 50 km range of a terrestrial fibre optic network.
To this end, a range of 100km is more than welcome and is set to reduce the digital divide.
Furthermore this will most likely catalyse a bandwidth price decrease and consequently increase broadband uptake. IEEE 802.22 does not specify implicit support for multi-hop networks, but it can be useful cases of mesh networking aiming to establish regional networks. The adoption of this standard alone cannot be regarded as a sole solution to the broadband challenge, for example the question arises as to what happens if multiple telecommunication players decide to all setup their own WRAN. Already deployment efforts aimed at implementing WRANS have revealed self-co-existence and the hidden incumbent problems as being the two major challenges facing wireless regional area networks. The IEEE 802.19 standard in the next subsection is formulated to address the self-co-existence problem.
2.6.2 IEEE 802.19. When multiple TVWS networks are brought together, the implication is that of multiple TVWS standards coexisting together and this creates a challenge. The IEEE 802.19 is thus formulated to handle the so-called self-coexistence problem which is associated with challenges posed by similar TVWS based systems in the same geographical area. To this
end, the standard specifies a radio technology that allows co-existence among dissimilar or in-dependently operated TV Band Device (TVBD) networks and dissimilar TVBDs [35, 135]. The IEEE 802.19 standard architecture comprises of the logical entities shown in Figure 2.9. IEEE 802.19 coexistence mechanisms exist to enable the co-existence of multiple TVBD networks in TV white spaces and minimize (and control) interference. Interference prevention is the major concern with the use of TVWS. Two independent co-existence mechanisms exist to support in-formation exchange relevant to the co-existence of TVBD networks in TVWS, one distributed and one centralized [263]. The former implements beacon transmission via a wireless broadcast channel and has a plug and play feature. The latter uses a centralized database which acts as a repository to the aforementioned information and is handled by a co-existence provider. The beacon approach has not been endorsed by FCC or OFCOM both of which have chosen the database approach as the only acceptable method.
The IEEE 802.19 standard points to the high possibility of integrating new TVWS networks with the back-haul networks that are already in existence and also to a mechanism for mitigating interference. On the other hand, this simplifies the task and cost of infrastructure development especially when both under and overlay networks are deployed. Moreover, over coexistence is de-sirable for short range transmissions. Intuitively, multiple coexistence scenarios will if well planned and implemented present business opportunities as this amounts to a market like environment.
The flip-side to this standard is that there may be undesirable overhead when network devices are burdened with coexistence support mechanisms. An interesting scenario may also be that the market may have the leeway to decide on which mechanism is best suited to the clientele.
Ultimately as a way of refining and improving this standard, more research still needs to be carried out to comprehend usage scenarios from a TVWS perspective in both the technical and business contexts.
Figure 2.9: IEEE 802.19 Architecture (Source [35])
Table 2.3 presents the logical entities of the IEEE 802.19 architecture with their corresponding functions.
Table 2.3: 802.19 Entities and their functions
Entity Function
Co-existence Manager (CM) Discovers other co-existence managers Makes co- existence decisions in order to solve co-existence problems among TVWS networks Supports interfaces for the co-existence discovery and information server
Supports o-existence commands and control information to co-existence enablers Co-existence Enabler (CE) Interface between CM and TVWS networks
Translates reconfiguring commands and sending them to TVWS network
Co-existence Discovery and Structures the information to be stored in a Information Server repository deployed over the Internet
Supports the discovery of CM by making the information relevant to co-existence accessible
In particular, the mechanisms proposed to deal with self-co-existence fail to solve the co-existence problem for cognitive radio systems operating under different radio communication standards.
2.6.3 ECMA 392. ECMA is a high-speed wireless networking standard for use in the Television White Spaces. The standard makes use of CR to avoid interference with licensed services and other incumbent users in compliance with the Federal Communication Commission (FCC) regulatory rules. The standard strives to deliver more robust wireless connectivity, by extending coverage range as well as offering cost effective networking solutions, both indoors and outdoors. To this end, targeted applications for this standard will encompass in-home high-definition multimedia networking and distribution as well as Internet access for communities.
2.6.4 Weightless. A TVWS standard for machine-to-machine communication using TVWS spectrum in the 450-800 MHz range [269]. Currently a new version 1.0 has been developed and will be used as basis for producing inter-operable products. From the perspective of the Weightless Special Interest Group (SIG) this is a ground-breaking cost-saving akin to Bluetooth in wireless personal area network [5]. Another group had previously argued that a common M2M standard for TVWS would drive down the cost of TVWS chipsets to less than 2 dollars. The merits of using TVWS are that the low frequency spectrum has a wider range of coverage up to about 10km as well as high building penetrative capability. Weightless is a global, open, FRAND-Z standard, meaning fair, reasonable, non-discriminatory and zero cost. The Weightless standard certainly complements the IEEE 802.22 standard for TVWS-based Wireless Regional Area Networks (WRANs), which has been designed to deliver 22-29 Mbps over a radius of 10-30 kilometrers. While 802.22 is designed to support high-bandwidth, high-power terminals and a relatively small number of users per base station, Weightless is aimed primarily at M2M services that require low bandwidth and low-power terminals and can serve many thousands of devices per base station. To this end, results of this standard have already been rolled-out such as (Iceni chip) of this standard. The chip is capable of tuning across the entire UHF TV white space spectrum (470 – 790 MHz), it draws negligible power while delivering reliable, secure, long range wireless connectivity for next generation M2M applications using the Weightless Standard [269] . One implication of this standard is that it is likely to bring to fruition the notion and idea of smart cities, for example in the transport sector, the quest for smart parking could be achieved through this standard. In the smart parking scenario each parking space is monitored and cars directed
to specific empty spaces as they enter a city or premise. Also in the health sector, telemedicine could be further advanced through this standard, for example sensor devices in pill dispensers, diabetes monitors, scales, heart rate monitors are all linked to external networks. This will be a welcome boost to the Internet of Things (IoT) market as it is estimated to be over a trillion US dollars in value and to enable tens of billions of connected devices by 2020.